Abstract: A process for the preparation of thermoplastic polyurethaneurea elastomers is disclosed. Accordingly, organic polyisocyanates (A) and a mixture (B) containing Zerewitinoff active hydrogen atoms, are reacted to yield an intermediate product. The intermediate product is then chain extended by thermal decomposition. Reactant (B) containsB1) 40 to 85 equivalent-% (relative to isocyanate groups in (A)) at least compound having an average of at least 1.8 to 3.0, preferably 2.0, Zerewitinoff active hydrogen atoms and a molecular weight of 400 to 10000, andB2) 10 to 60 equivalent-% (relative to isocyanate groups in (A)) of at least one specifically recited tertiary hydroxyl compounds.